Resistance or fuse wire



Patented May 8, 1945 v RESISTANCE. OR FUSE WIRE Cecil Spencer Sivil, Roselle, N. J., assignor to Baker & Company, Inc., Newark, N. J., a corporation of New Jersey I No Drawing. Application July 8, 1943,

' Serial No. 493,946

3 Claims.

This invention deals with electrical resistance trical resistances suitable for instance in the ignition of explosives such as fuse or bridge wires in blasting caps, detonators, or the like.

Heretofore such resistance wires for igniting or settingofi explosives usually consisted of an aly of platinum-iridium containing from 10% to 20% iridium, the alloy of 80% platinum and 20% iridium generally being preferred. Because of the high cost of such alloys attempts have been made to cheapen the cost of such wire by substituting part or all of the precious metal with base metals, resulting however in the production of wires which tended to corrode under the influence of the atmosphereor the match com-- pounds'in which they were embedded, which made such wires unfit for use unless used reasonably soon after production of thelwire or insertion in the fuse. Other attempts to replace all or part of the expensive iridium in such platinum-iridium alloys have been made, but such attempts were limited to the incorporation or substitution of other high priced precious metals andthus did not afford satisfactory relief from the high cost of the platinum-iridium alloy resistance wires for fuses.

It is one object of my invention to produce a resistance wire for use. in igniting explosives, as in blasting caps, detonators or the like, which shall consist substantially of precious metals only and shall have low specific gravity, high electrical resistance and satisfactory breaking loads or tensile strength to take the place of fuse wire of platinum-iridium alloys heretofore in general use in setting 01f explosives, and which while having characteristics similar to those of such platinumiridium wires shall be of considerably lower cost. It is another object of this invention to provide a platinum metal electrical resistance wire for other uses requiring electrical resistance and corrosion resistance. will appear from the description thereof hereinafter following.

This application is a continuation in part of my earlier application Serial No. 288,572 filed August 5, 1939.

I have discovered that electrical resistance wires such as fuse wires achieve the hereinbefore stated objects when constructed of alloys of platinum r wires and is concerned in particular with elec- Other objects of the invention palladium and at least one metal of the group ruthenium and rhodium, in particular ruthenium. The alloys utilized and found suitable for the purpose contain from 10% to 80% platinum, [from 12% to 89% palladium, and from 1% to 15% of at least one metal of the group consisting of ruthenium and rhodium. The electrical resistance wires of the invention can be divided into two groups. One group has a relatively high platinum content and correspondingly low palladium content, such as alloys containing from.

% to 80% platinum, from 12% to 30% palla- 4 dium, and from 1% to 15% ruthenium, such "for instance as alloys of platinum 25% palladium (10% ruthenium, or of platinum 24% palladium 6% ruthenium, or of 74% platinum 20% palladium 6% ruthenium, or of platium 14% palladium 6% ruthenium. The'other group has a relatively low platinum content and correspondingly high palladium content'suchas alloys containing from 10% to less'than 60% platinum, preferably not more than about 55% platinum, from more than 25 palladium to 89% palladium and from 1% to 15% ruthenium or rhodium, such for instance as alloys of 55% platinum 30% palladium 15% ruthenium, or of 55% platinum 35% palladium 10% ruthenium, or of 50% platinum 47% palladium 3% ruthenium, or

of 40% platinum 57% palladium 3% ruthenium,"v

or of 30% platinum 67% palladium 3% ruthenium, or of 20% platinum 77% palladium 3% ruthenium, or of 10% platinum 87% palladium.

3% ruthenium.

In all cases the platinum content must not fall below 10% and should not exceed 80 %,'and while the palladium content should not fall below 12% and must not exceed 89% it should preferably exceed 25% and comprise in particular at least 30%. Theruthenium content, like the rhodium content, must not fall below 1% nor exceed 15% and preferably runs from 3% to 10%. The most suitableand advantageous fuse wire is constructed of alloys of 25% to 55% platinum, 30% to 74% palladium, and 1% to 10% ruthenium, and shall be of alloys of 40% to 55% platinum 45% to 59% palladium and 3% to 10% ruthenium. In particular I recommend an electrical resistance wire of about 47% platinum about 57% palladium about 3% ruthenium.

The following table will illustrate some of the for electrical resistance wires of 80% platinum-p 20% iridium alloy and. certain electrical resist-I ance wires of the invention with high platinum and low palladium content on the one hand and 1 low platinum and high palladium content on the other hand. i r

Breaking Composition, load, grams 7 Resistivity Density g g? per cent atSOOghmsh ohms/IniLi't. {gt-I00. I I

Pt Ir 80 20 110-120 200 21.6 1,950

Pt Pd Ru 87 3 70 153 I 12.6 1, 575 77 3 74 169 13.2 1, 595 67 3 76 190 13.9 ,1, 620 57 3 77 200 14.5 1,640 47 3 83 212 15.4 1, 660 37 3 to 220 ;16.-4 .1;680 24 6 140 250 17.3 1,700 74 20 6 128 243 17.8 710 14 6 70 235 18. 5 1, 730

Platinum palladium ruthenium and rhodium are, like iridium, members of the platinum group and. possess consider-able corrosion resistance. Palladium 'as' well as ruthenium andrhodium has a specific gravity considerablyfil'ower than that =of either :;platinum or iridium and :the -;electrica1-resista'nce Wiresnfthe "invention possess, therefore, a, lower density than the electricalresistance wire of "platinum-iridium alloy. In the high platinum content :alloy wires of the invention the tensile strength and electrical resistance are higher than in-thelowplatinum content alloy wires of the invention. :All'resistance wirespossess-high .corrosiorilresistance zasyrequired in the case of fuse wires;

"llhe electrical resistance wires of relatively low platinum and high'palladium content represent particularly desirable electrical resistance wires in that they :have an especially low specific gravity.

'Ihey Zcontain :considerably less platinum thanthe platinum-iridium wires of the prior art and while they ipos'sessll'ess tensile strength and lower electrical resistancethan either theplatinum iridium wiresiofithe prior art or the wires of the invention having a high aplatinum content they will :have' suffi'cient tensile'strength for the purpose and the particular electrical resistance act the ,individual wires can "be controllediby'varying the diameter ofthewire; -F!use!or"bridge:wires for blasting caps for'instance usually have an electrical resistance of 'i3ll0yphms'per yard. A fuse wire of 80%;platiance has a diameter of 0.0015". A fuse wire of 40% platinum 57% palladium and 3% ruthenium, representing the best embodiment of electrical resistance wires of platinum palladium ruthenium 5 alloy having a low platinum content, has such resistance of 300 ohms/yd. when the wire is given vadiameter of 0.0014". Whenever, therefore, the electrical resistivity in terms of ohms/mil. ft. is lower for any alloy within the scope of the inven- '10 tion than for 80% platinum-20% iridium the same ohms/yd. resistance can be obtained by decreasing the diameter of the wire, :and vice versa,;

so that in actual practice electrical resistance wires can be produced from the range of. alloys 15 stated identical with that of a fuse wire of 80% "platinum--'20% iridium alloy now, in use, The

breaking load of the individual wires, while lower than that'of theprior'art wire of 80% platinum ,j20'%' iridium alloy, is, nevertheless, suflicient for 20 the purposes contemplated, particularly where ,the

".p1atinum'content does not fall below about 25%;

While one ounce of 80% platinum-20% iridium alloy will furnish only 4520 ft. at 300-ohins/yd., one ounce of 87% palladium10% platinum-3% 25 ruthenium alloy-will furnis'h 10,500 ft. ati'300 ohms1yd.,:and:.one enticed-57% palladium- 40% platinumruthenium will furnish 7300 it. at 300 ,ohmsZ-yd; On lth'eother hand, for instancega wire of 70% platinum24%"palladium'and 6% ru- 30 then'ium will have an electrical resistance of 3.00

ohms/yd. when it iswgiven a diameter1050:0016",

e in which case i1punce'ofalloywilli'furnish4-535 it.

of'wire.

The "electrical resistancewlire may .beused 35 Wherevera corrosion resistant wire is desired ior the purpose of resisting thepassageof an electri-.

cal current or producinga potential drop of some desired amount. Although it is specifically de- "jsignedffor'use asa fuseror bridge "-wireior-the set 40 ting :off of explosives, it may also' be "used, for instance'as resistance wire in the' Wheatston'e bridge,-

as in gas analyzers-or the like.

What I1claim'is: i e 1. Electrical resistance wire of .an alloy of 45, platinum palladium and "ruthenium comprising from 25% 'to 55%flplatinum, 30%to 74% Palladium,-and 1'% to 10% ruthenium;

"2.Electrical resistance wire'of an :alloy of plati- PIlllII-i palladium and ruthenium comprising-from I30 40% to 55% platinum, 45% to'59% palladium, and

3% to 10% ruthenium. V i BR'Electrical resistance wire of an alloy of platinum palladium and ruthenium comprising about 40% platinum, about 57% palladium, and about num--.-20% 1rr1d1um :alloy possess ng such esist- ?1 emum CECIL-SPENCER srvrn 

